1. Field
The present disclosure relates to technology for smoothly transmitting and receiving Session Initiation Protocol (SIP) messages in a network, and more particularly, to a system and method for transmitting and receiving SIP messages.
2. Discussion of Related Art
Voice over Internet protocol (VoIP) technology, also referred to as Internet telephony, has the purpose of providing a voice call service through the Internet. VoIP has merits in that it is possible to provide a voice call service at low charge and to easily provide various multimedia services using the voice call service. Thus, VoIP has been rapidly spreading in recent times.
As one base protocol for such an Internet telephony service, etc., there is SIP. SIP is a protocol that has been suggested by the Internet engineering task force (IETF) to establish and terminate a multimedia session. Due to its simplicity, SIP can be easily developed and implemented. Also, since SIP was designed for the Internet, it is possible to easily provide various multimedia services of the Internet.
In a VoIP service in which the aforementioned SIP is employed, a terminal generally exchanges messages with a proxy server using User Datagram Protocol (UDP). However, when the terminal is behind a firewall, etc., UDP packets cannot traverse the firewall, and it is impossible to provide the service.